The effect of mannan-binding lectin on opsonophagocytosis of Neisseria meningitidis.
Mannan-binding lectin (MBL), an acute phase protein with a structure and a function very similar to that of C1q, is known to act as an opsonin binding to a number of microorganisms. In order to investigate the effect of MBL on the phagocytic killing of meningococci, a serogroup B meningococcal strain (H44/76) and its unencapsulated variant v24, as well as a serogroup A meningococcal strain were opsonized with MBL (purified from normal human plasma at the State Serum Institute, Denmark) and used in a phagocytic killing assay at a density of 7 x 10(3) CFU/ml. Polymorphonuclear cells (PMNs) from one healthy donor were isolated by density gradient centrifugation over Percoll and added to the system (7 x 10(6) cells/ml). In a first set of experiments without addition of serum or complement, no influence of MBL was observed on the killing of any of these strains. Addition of MBL to non-opsonized bacteria of the serogroup A strain did not result in enhanced killing either; on the contrary, the growth of this strain increased significantly when a high MBL concentration (40 micrograms/ml) was used in the presence of PMNs. Further investigations were performed using sera of five individuals with late complement component deficiency (LCCD) and a concomitant MBL deficiency, vaccinated with a tetra-valent (ACYW135) meningococcal capsular polysaccharide vaccine. Pre- and post-vaccination sera (50% final concentration) were tested against a group A strain opsonized or not with MBL. In only one patient was there a moderate increase of killing of the opsonized bacteria after vaccination compared to pre-vaccination serum. Our results suggest that MBL may not play a significant role in the opsonophagocytosis of meningococci, irrespective of its binding to unencapsulated and serogroup A strains.
Drogari-Apiranthitou
M
M
Department of Medical Microbiology, University of Amsterdam, The Netherlands.
Fijen
C A
CA
Thiel
S
S
Platonov
A
A
Jensen
L
L
Dankert
J
J
Kuijper
E J
EJ
D001428:Bacterial Vaccines / Q000008:administration & dosage; D002352:Carrier Proteins / Q000494:pharmacology*; D037222:Collectins; D003114:Colony-Forming Units Assay; D015922:Complement C1q / Q000276:immunology; D003165:Complement System Proteins / Q000172:deficiency*; D006801:Humans; D037102:Lectins / Q000494:pharmacology*; D008351:Mannans / Q000494:pharmacology*; D009345:Neisseria meningitidis / Q000187:drug effects* / Q000276:immunology; D009895:Opsonin Proteins / Q000032:analysis; D010587:Phagocytosis / Q000187:drug effects* / Q000276:immunology; D014611:Vaccination
D001428:Bacterial Vaccines; D002352:Carrier Proteins; D037222:Collectins; D037102:Lectins; D008351:Mannans; D009895:Opsonin Proteins; D015922:Complement C1q; D003165:Complement System Proteins